Apparatus for spinning rayon



y 1941- A. s. BROWN 2,242,999 v APPARATUS FOR SPINNING RAYON 7 Filed March 11, 1958 2 Sheets-Sheet 1 INVENTOR 4 ATTORNEYS y 1941- A. s. BROWN 2,242,999

APPARATUS FOR SPINNING RAYON Filed March 11, 1958 2 Sheets-Sheet 2 INVENTOR 144/110 Sir/y Erna/11 BY C D ATTORNEYS Patented May 20, 1941 APPARATUS FOR SPINNING RAYON Alfred Seely Brown, Hamilton, N. Y., assignor to Skenandoa Rayon Corporation, Utica, N. Y., a

corporation of Delaware Application March 11, 1938, Serial No. 195,363

3 Claims.

This invention relates to the manufacture of artificial silk or rayon and, more particularly, to a new and improved form of spinning pot for use in such manufacture according to the centrifugal spinning bucket system.

Objects of the invention include the provision of a spinning pot having a novel and advantageous shape, configuration, size and relation of the elements of its interior surface, which tends to improve the quality and other properties of rayon yarn spun therein.

The use of a spinning pot according to my invention also tends to produce a yarn cake looser in structure, and better adapted for processing and subsequent treatment, than cakes spun in other forms of pot. It may also produce a yarn cake adapted to be dried with more uniform shrinkage of the yarn in different parts of the cake.

Other objects of the invention include the provision of a spinning pot of such form, construction, proportion and relation of its elements that yarn cakes spun therein tend to possess improved uniformity of denier, stretch and other textile properties of the yarn from all parts of the cake, after the cake has been processed and dried and the yarn is completed and ready for sale or fabrication.

Although useful in connection with other processes, under proper conditions, the spinning pot herein described and claimed is particularly advantageous, I have found, for use in connection with the process and apparatus for treating rayon yarn which forms the subject-matter of my copending application, filed concurrently herewith, Serial Number 195,364, filed March 11, 1938.

Other objects of the invention will appear from the drawings and following description, and from the claims.

In the accompanying drawings:

Figure 1 is a plan View of, and Figure 2 is a vertical sectional view through, a spinning pot embodying the invention;

Figures 3 and 4 are detailed views showing the form and configuration of inward projections, or ribs, which I sometimes call "slats, on the inner surface of the pot shown in Figures 1 and 2;

Figure 5 is an enlarged and merely diagrammatic view of a part of a spinning pot like that of Figures 1 and 2, illustrating the manner in which the yarn is spun therein;

Figure 6 is a plan view of another spinning pot, with ribs or inward projections upon the inner surface thereof, embodying the invention;

Figure 7 is an enlarged and merely diagrammatic View of: a part of a spinning pot like that of Figure 6, illustrating the manner in which the yarn is spun therein; and

Figure 8 is a diagrammatic plan view of one rib or slat, for the purpose of illustrating and defining various parts and dimensions thereof, which will be hereinafter referred to in detail.

I am aware that it has heretofore been proposed to employ rayon yarn spinning pots of generally cloverlea or sinuous interior horizontal crosssection; as, for example, pots molded or having inserts, generally convex in contour, to provide the desired conformation. Examples are German Patent No. 583,335, granted September 1, 1933, and French Patent No. 757,038 granted October 2", 1933; while in United States Patent No. 1,990,617, to Sanders et a1., granted February 12 1935, there is proposed a spinning pot having closely-spaced vertical ribs, for a different purpose.

I have found that such clover-leaf and other heretofore-proposed shapes and forms of spinning pot are unsatisfactory for several reasons and fail, as a practical matter, to solve the difiiculties actually encountered in commercial operation.

As a result of my tests and experiments, I have discovered that the maximum allowable radial depth of any projection or rib, in a spinning pot, is, as a practical matter, limited by the permissible variation in the centrifugal force acting upon adjacent portions of the yarn. In order to minimize such variation, or at least, to keep it within permissible limits, say not more than of the order of about 10 per cent, I have found it desirable that, for example, in a pot of 7-inch greatest internal diameter, operated at a normal speed, the radial extent of the inward projections should not exceed something of the order of about of an inch. Excessive variations in centrifugal force tend to cause the formation of shiny spots in the fabric and increase the tendency to the formation of crossed threads in the yarn cake structure; and I have discovered that ribs of too great height cause such excessive variations. the inward projections are too close together, the thread does not sufficiently follow the contour of the pot during spinning, and the desired result is not attained. Moreover, I have found that the use of rounded or convex projections, such as have been heretofore proposed, is apt to cause rapid decrease in the tendency of the thread to follow the contour of the pot, and the desired result is not attained. Because of these and other limitations and difficulties, the shapes and forms of spinning pots heretofore proposed have been found unsatisfactory for practical commercial operation.

By a long series of tests, investigations and experiments, I have discovered that the properties of the yarn may be substantially improved, a greater length of yarn may be spun around the circumference of the pot, especially at the outside of the cake, to give what I call an excess length of yarn in the outside of. the cake. and

other advantageous results attained, by the use of inward projections or ribs in the pot, of proper number, height, size, shape, proportion and relation; and it is such a spinning pot which forms the subject-matter of this application. I have found that such an excess or extra length of yarn, spun into the cake at or near the outer periphery thereof, allows the yarn to shrink with greater uniformity during subsequent processing and drying, without placing the yarn under undue or uneven tension. The result is the formation of a yarn cake in which the yarn from the inside and outside tends to be more uniform in denier, crinkle, shrinkage and other physical and textile properties, as well as in dyeing quality.

I have discovered, also, that in order to overcome a tendency to non-uniformity in different parts of the cake, the extra yarn length, which should be spun into the yarn cake, should, in general, be as great as possible, and should preferably exceed about 10 per cent. of the entire length of the yarn which would be spun in the outer part of the cake if the ribs or slats were absent. This extra length of yarn is preferably greatest at the outside of the cake, and may decrease toward the inside, since the resistance to yarn shrinkage also diminishes toward the inside of the cake. I have also found that, for best results, the extra length of yarn spun into the outer part of the yarn cake should be at least sufficient, and preferably more than sufficient, to permit natural shrinkage of the yarn during processing and subsequent drying, so that the yarn in the cake is enabled to shrink. without undue tension or stretching. By the use of my invention, I have found it possible to spin as much as of the order of 20%, or even more, of extra length into the yarn at the outside of the yarn cake, without substantially harmful'variation in the centrifugal force applied to the yarn between the edges of the ribs and the wall of the pot, and without injurious formation of crossthreads during a spinning period of desirable and satisfactory duration. r

, I have also discovered that it is possible, according to my invention, if aproper design, configuration; and proportion of the inward projections or ribs in the spinning pot is employed, to spin a yarn cake which is relatively soft and porous, and permits more ready access of processing fluids to all parts of the cake. The invention also permits control of the rigidity of the cake, thereby facilitating subsequent processing. Referring now in greater detail to Figures 1 and 2 of the drawings, the spinning pot is shown at Ill. Upon its interior surface it is provided with a series of inward projections or ribs I I. In the construction shown, these extend from top to bottom of the pot, and may be slightly tapered from the bottom toward the top, so that the spun cake may be readily withdrawn from the pot. What I have found to be a particularly advantageous shape for these projections is shown in the drawings. The faces l2 and I3 are, as shown, concave toward the interior of the pot. In the drawings, the direction of rotation is indicated by the arrows as being counterclockwise, and the leading faces I2 of the projections l I are shown less steep than the trailing faces I3. Since. the rotation of the pot tends to throw the yarnagainst the leading face of the rib, there is a tendency for the yarn to pack in front of this face and form a region of kinky or excessively curlyyarn. This may be avoided by making the leading faceless steeply sloped; and, I have found that it is, in general, advisable to make the trailing edge more steeply sloped than the leading one.

Although some of the advantages of the invention may be realized by the use of projections or ribs which are triangular in cross-section, I have found that the full advantages of the invem tion are not usually attained unless the faces of the ribsare concave toward the interior of the pot, in the manner shown in the drawings, except at the vertex of the slat. The vertex of the slat is preferably slightly rounded off to remove the sharp edge which would otherwise exist at that point, and to prevent possible damage to the yarn.

I have found that in a pot of about seven inches diameter, a desirable and satisfactory radius of curvature for the faces of the ribs is 1.5:05 inches. I have also found that the curve of the slat faces preferably is not tangential to the main circular periphery of the spinning-pot.

If the curve of the rib faces is tangential to the main circular periphery of the pot a number of difliculties have been found to be encountered: For moderate radii of rib-face curvature, a loss of cake softness, a decrease in extra yarn length, and an increase in slat volume result, all of which are generally undesirable; for small radii of ribface curvature, the formation of an excessively and undesirably acute rib vertex (for practically useful slat heights) I have further discovered that the full advantages of the invention are not realized unless the number of ribs distributed over the inner periphery of the spinning-pot lies within a certain limited range of suitable values, hereafter defined. Reasons for this are that the. extra yarn length spun into the cake (within the range of practical pot designs) is essentially proportional to the number of ribs or slats; the ability of the yarn to utilize the extra yarn length spuninto the cake depends upon the spacing of the ribs, hence upon the number of ribs; the softness (and porosity) spun into a cake depends upon the spacing of the ribs, hence upon the number of ribs; the

ability of the yarn to follow the shape of a rib or slat depends upon the spacing of the ribs, hence upon the number of ribs; the permissible length of the spinning-period depends upon the spacing of the ribs, hence upon the number of ribs; and the volume occupied by the ribs'land therefore not available for yarn) depends upon the number of ribs.

By the extended series of tests and experiments previously referred to, I have discovered that, in order to secure the advantages and attain the results previously stated, the number and dimensions of the ribs or slats may be determined and correlated, within practical limits, as follows:

1. The number of ribs, N, may be determined I by the following approximate formula:

The number of the ribs must be an integer.

2. The radial depth of the ribs is preferably kept as small as possible, and, ordinarily, should not exceed about fifteen per cent. of theradius of the spinning-pot. For practical purposes. the

radial depth of the ribs may be determined by the formula:

H=K1'R where:

H is the radial depth of the rib in inches R is the radius of the spinning-pot in inches K1 is a constant=0.10:0.02.

Restriction of the radial depth of the ribs to substantially the limits imposed by that formula has been found advantageous in order to prevent undue variation in the textile characteristics of adjacent lengths of the yarn, and to reduce tendency to the formation of cross-threads during the spinning-period. It is obvious that the use of a radial depth of rib less than that given by the formula just stated is satisfactory from this point of view.

In order to show and define certain of the dimensions to which reference is made in the foregoing formulae, and others to follow, reference may be had to Figure 8, in which the parts and controlling dimensions of a rib or slat are shown as follows:

m=pot radius, R I A B chord height of rib whose base is (a+ b) E=radial depth of rib, H

n, rt=radii of curvature of rib faces a=base of trailing face of rib b=base of leading face of rib The rib height, h, is not always equal to the radial depth, H, of the rib measured from the main circular pot periphery. The height h must be increased by the chord height of the slat base, a-l-b, in a circle whose radius is that of the spinning-pot, and must be decreased by the rounding off of the edge at the rib vertex in order to obtain the radial depth, H. In general, these two dimensions, h and H, are very nearly equal.

The shape of the ribs is generally triangular, with the additional considerations that: the leading face of the rib is preferably less steeply sloped with respect to the main circular periphery of the pot than is the trailing face; and the rib faces are preferably curved, concave toward the pot interior, a satisfactory radius of curvature being 1.5105 inches.

The most suitable proportions and dimensions of the ribs, more particularly with reference to the dimensions as defined in connection with Figure 8, may be determined from the following consider ati ons (l) The lower limit of a, the base of the trailing face of the rib, is determined by the ability of the yarn to follow the contour of the trailing face. This dimension is best defined by reference to the ratio of a to h. When 11/71. is too small the yarn no longer follows the rib face. For satisfactory results, the lower limit of a/h is about 0.5, and the preferred range of a/h values is from about 0.5 to about 1.0.

(2) The lower limit of b, the base of the leading face of the rib, is determined by the value of b/h below which the yarn forms kinks or curlers against the leading face of the rib. For satisfactory results the lower limit of b/h is about 1.0, and the preferred range of b /h values is from about 1.0 to about 2.0.

(3) For a given height, h, the rib base, a+b, is preferably as small as possible in order to give high extra yarn length; low rib volume; and high degree of softness of the cake.

I have further found that under certain conditions it is sometimes advantageous to use alternately larger and smaller ribs or slats, as shown in Figures 6 and '7. This has been found to cause even greater softness of the cake than when all the ribs have the same size and height.

If the ribs have sensibly the same size the total number of ribs is given by the formula for N, as stated above. If the difference between the rib sizes is great, the number of larger ribs is given by the formula for N.

A specific example of suitable dimensions and proportions for the ribs II, for the construction shown in Figures 1 to 4, has been found to be as follows, in an illustrative case:

R Radius of the pot: 3.5 inches w=Angular pot velocity: 7200 R. P. M.

N=number of projections or ribs: 12

h=Height of each rib: 0.375 inch to the cord subtending its base;

H Radial depth of each rib: 0.37 inch b/h=Slope of the leading face: 1

a/h=Slope of the trailing face: 0.67

Length of the cord at the base of each rib:

0.625 inch Radius of curvature of each face of the rib:

1.5 inches.

With the foregoing dimensions and proportions of the pot and ribs, 1 have found that the extra length of yarn spun into the cake at the outer periphery, over and above the length of yarn in a cake spun in a circular spinning pot of the same radius, is sufficient to permit substantially uniform shrinkage of the yarn throughout the cake and the other advantages of the invention, as previously stated, are substantially realized in the example given.

The apparatus herein described includes the best embodiments of the invention now known to me, but it is to be understood that the invention is not necessarily or specifically limited thereto, in all cases, but, under suitable conditions, may be carried out in other ways without departure from its spirit, and within the proper scope of the following claims.

I claim:

1. A spinning pot for spinning a rayon yarn cake by the centrifugal spinning system, comprising a hollow bucket portion having a diameter of the order of about seven inches, in which the yarn is to be spun and collected, and a plurality of generally V-shaped inwardly-projecting substantially vertical ribs arranged at intervals about the inner surface of the pot and so shaped as to present toward the cake a plurality of acute, substantially triangular, pointed projections adapted to form spaced, reentrant angular recesses or notches extending substantially vertically in the outer periphery of a yarn cake spun in the pot; the number of said ribs being not less than nine or more than fifteen; the radialdepth of each rib being not greater than about three-eighths of an inch; the length of the cord at the base of each rib being between about one and one-half and three and one-half times the radial depth of the rib; and the slope of the leading face of each rib being less than the slope of the trailing face thereof, with respect to the periphery of the spinning pot, whereby a substantial excess length of yarn is spun into the outer layers of the cake without detrimental variation in centrifugal force applied to the yarn, and while the yarn in the outer layers of the cake substantially follows the contour of the inner surface of the spinning pot.

ing a substantially circular bucket portion provided upon its interior surface with a plurality of projecting ribs the total number of which is between about 0.03 and 0.05 times the product of the radius of the pot ininches multiplied by the square root of the angular velocity of operation for which the pot is designed, in revolutions per minute; the radial depth of which is between 0.08 and 0.12 of the radius of the pot in inches; the faces of which are concave toward the interior of the pot, with a radius of curvature between 1 and 2 inches; of which the ratio of the base of the trailing face to the height is between about 0.5 and 1.0; and of which the ratio of the base of the leading face to the height is between about 1.0

and 2.0.

f 3. A centrifugal spinning pot for spinning a cake of rayon yarn by the centrifugal bucketspinning system, which comprises a hollow pot portion for receiving and collecting the yarn and;

where H is the radial depth of the rib in inches,

R is the radius of the spinning pot in inches, and K1 is a constant equal to 0.10:0.02; the faces of said ribs being concave toward the interior of the spinning pot and having a radius of curvature of approximately 1.51 105 inches; the ratio a/h for said ribs lying between about 0.5 and 1.0; and the ratio b/h for said ribs lying between about 1.0 and 2.0. I

ALFRED SEE-LY BROWN. 

